Processes that cause diffuse calvarial lesions are generally related to systemic or metabolic processes, metastases, or Paget’s disease. The imaging appearance is quite variable, with some diseases causing lytic lesions, others causing sclerotic lesions, and still others giving a mixed pattern – even one that may change over the course of the disease, such as in Paget’s disease. Often differentiating these lesions is not a diagnostic dilemma because of characteristic appearance (Paget’s disease or diffuse metastases), or relevant clinical history.

Paget’s Disease

Paget’s disease of bone is a fairly common skeletal disease of uncertain etiology characterized by excessive and abnormal remodeling of bone with an imbalance between bone resorption and formation. The calvarium and skull base are commonly involved, as are the spine and pelvis. Basilar invagination can occur in the setting of skull base involvement. Although not initially a diffuse lesion, Paget’s disease can progress to involve much of the calvarium.